The present application relates to a flexible substrate, a mounting method of a flexible substrate, and a lighting system.
In the related art, a so-called ring lighting system in which a plurality of LEDs (Light Emitting Diode) with small power consumption is disposed in a ring shape is used for lighting of a CCD camera in an image processing apparatus or lighting for observation in a microscope. In the ring lighting system, the LEDs are disposed around an object lens to radiate light from all directions or angles to an observation object such that an image is made easy to be observed by making shades of fine prominences and depressions on the surface of the observation object such that the contours appear.
A plurality of LEDs is disposed in a ring shape in manufacturing of the ring lighting system. Further, the LEDs may not be disposed only in the ring shape, but with inclination angles of generally 0° to 90° to radiate light to observation objects, in accordance with the surface condition of each of the observation objects. Therefore, it is necessary to mount LEDs on inclined surface with angles in the process of mounting light sources. In the related art, an effort for another mounting method different from mounting on common flat substrates is demanded for automatic equipment.
For this configuration, as a present general mounting method, for example, as disclosed in Japanese Patent No. 2975893, a C-shaped flexible substrate with a notch shaped and sized to fit to a conical surface of a ring-shaped part with the conical surface is prepared first. Thereafter, LEDs are mounted on the upper flat surface of the substrate and then the LEDs are disposed at predetermined angles and positions of a ring by bending the substrate to couple the notch of the substrate and attaching the substrate to the conical surface of the ring-shaped portion.
However, when the density of the mounted LEDs increases, the tips of the LEDs become smaller than the radius of curvature of the flexible substrate in curving, such that the LEDs interfere with each other and it is not easy to bend the flexible substrate. Further, the interference between the LEDs or bending the soldered joint of the printed substrate causes stress in the soldered joint. Accordingly, there is a problem in that cracks are generated in the soldered joint and bad electrical contact is generated.
In order to remove the bad electrical contact due to the cracks generated in the soldered joint, in Japanese Unexamined Patent Application Publication No. 2008-78066 described below, a structure having a specific structure has been proposed.